2''-O-galloylhyperin as a novel adjuvant to reduce imipenem resistance in multidrug-resistant Pseudomonas aeruginosa: transcriptome-based mechanism of iron homeostasis disruption.

Imipenem, a critical antibiotic for treating multidrug-resistant Pseudomonas aeruginosa, now faces severe resistance from this pathogen. This study investigates the synergistic effects and underlying mechanisms of the combination of 2''-O-galloylhyperin with imipenem against P. aeruginosa. 2''-O-galloylhyperin showed no significant effect on the growth curve of strain 18102011 and its transconjugant D2011, while reducing the MIC of imipenem against this strain by 4-fold (FICI ≤ 0.5, synergy). This compound upregulates the citrate synthase gene gltA, and downregulates the aconitase gene acnA, enhancing citric acid synthesis while inhibiting its dehydration to cis-aconitase acid. Citric acid chelates Fe2+/Fe3+, reducing iron bioavailability, disrupting electron transfer, and increasing intracellular ROS levels in P. aeruginosa 18,102,011. Additionally, 2''-O-galloylhyperin reduces the activity of the carbapenemase KPC-2. These findings highlight its potential as an adjuvant to enhance imipenem efficacy against P. aeruginosa infections.